Smoke rises from the al-Mishlab district at Raqqa’s southeastern outskirts, Syria June 7, 2017. REUTERS/Rodi Said(Reuters) United Nations war crimes investigators said on Wednesday that intensified coalition air strikes supporting an assault by U.S.-backed forces on Islamic State’s stronghold of Raqqa in Syria were causing a “staggering loss of civilian life”.

The Syrian Democratic Forces (SDF), a group of Kurdish and Arab militias supported by a U.S.-led coalition, began to attack Raqqa a week ago with the aim of taking it from the jihadists. The SDF, supported by heavy coalition air strikes, have taken territory to the west, east and north of the city.

Paulo Pinheiro, chairman of the U.N. Commission of Inquiry also told the Human Rights Council that 10 agreements between the Syrian government and armed groups to evacuate fighters and civilians from besieged areas, including eastern Aleppo, “in some cases amount to war crimes” as civilians had “no choice”.